Effect of berberine on positive transcription elongation factor b expression in diabetic rat retinas

AIM To investigate the positive transcription elongation factor b(P-TEFb)expression and the effect of berberine on diabetic retina of the rat.METHODS Type 2 diabetes mellitus rat models were induced by injection(ip)with streptozotocin(STZ)35 mg·kg~(-1)and 2 wk later followed by a high-carbohydrate/ high-fat diet for 14 wk.From wk 17,the rats were divided into 7 groups with 10 rats in each:age-matched non- diabetic control rats(group A)that neither received STZ nor the high-carbohydrate/high-fat diet;16-wk diabetic rats without any drug treatment(group B);diabetic rats treated with berberine at a dose of 75,150 or 300 mg·kg~(-1)every day(group C,group D,and group E,respectively):diabetic rats treated with fenofibrate at a dose of 100 mg·kg~(-1)or rosiglitazone at a dose of 4mg·kg~(-1)every day(group F and group G both served as positive control).After 16 wk treatment,the retinal structure was observed with hematoxylin-eosin(HE) staining and P-TEFb(cyclin-dependent kinases 9(CDK9)and cyclin T1)protein expression was detected by immunohistochemistry.RESULTS The retinas of control group were thicker than those of other 6 groups.After 16 wk treatment of middle-,high-dose berberine and rosiglitazone,the diabetic retinas showed increase of thickness but no difference in retinal structure among all groups.Middle-,high-dose berberine and rosiglitazone promoted significantly CDK9 and cyclin T1 expression in diabetic retinas(P0.01),but low-dose berberine and fenofibrate showed no effect on CDK9 and cyclin T1 expression.CONCLUSION Berberine modulating P-TEFb level in diabetic retina may probably be one of the mechanisms to ameliorate retinopathy induced by STZ and the high-carbohydrate/high-fat diet.